Disk drive having a top cover channel vented to a central cavity via a hole through a bottom land

ABSTRACT

A disk drive has a disk drive base with a central cavity surrounded by a peripheral wall. The disk drive also includes a top cover attached to the disk drive base and disposed over the central cavity to define a disk drive enclosure. A disk is rotatably attached to the disk drive base within the central cavity, and is disposed within the disk drive enclosure. The top cover has a central top face that defines a central top face plane. A foil seal is adhered to the central top face. The central top face of the top cover includes a first channel that has a bottom land that is depressed towards the disk relative to the central top face plane, and the foil seal covers the first channel. The first channel is vented to the central cavity by a hole through the bottom land of the first channel.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is related to co-pending U.S. patent application Ser.No. 14/666,184 filed on Mar. 23, 2015, entitled “DISK DRIVE HAVING A TOPCOVER CHANNEL VENTED TO A CENTRAL CAVITY VIA A PERIPHERAL CLEARANCEGAP,” to Nicholas D. Smyth, which is hereby incorporated by referencedin its entirety.

BACKGROUND

The typical hard disk drive includes a head disk assembly (HDA) and aprinted circuit board assembly (PCBA) attached to a disk drive base ofthe HDA. The HDA includes at least one disk (such as a magnetic disk,magneto-optical disk, or optical disk), a spindle motor for rotating thedisk, and a head stack assembly (HSA). The PCBA includes electronics andfirmware for controlling the rotation of the spindle motor and forcontrolling the position of the HSA, and for providing a data transferchannel between the disk drive and its host.

The spindle motor typically includes a rotor including one or more rotormagnets and a rotating hub on which disks are mounted and clamped, and astator. If more than one disk is mounted on the hub, the disks aretypically separated by spacer rings that are mounted on the hub betweenthe disks. Various coils of the stator are selectively energized to forman electromagnetic field that pulls/pushes on the rotor magnet(s),thereby rotating the hub. Rotation of the spindle motor hub results inrotation of the mounted disks.

The HSA typically includes an actuator, at least one head gimbalassembly (HGA), and a flex cable assembly. During operation of the diskdrive, the actuator must rotate to position the HGAs adjacent desiredinformation tracks on the disk. The actuator includes a pivot-bearingcartridge to facilitate such rotational positioning. The pivot-bearingcartridge fits into a bore in the body of the actuator. One or moreactuator arms extend from the actuator body. An actuator coil issupported by the actuator body, and is disposed opposite the actuatorarms. The actuator coil is configured to interact with one or more fixedmagnets in the HDA, to form a voice coil motor. The PCBA provides andcontrols an electrical current that passes through the actuator coil andresults in a torque being applied to the actuator.

Each HGA includes a head for reading and writing data from and to thedisk. In magnetic recording applications, the head typically includes aslider and a magnetic transducer that comprises a writer and a readelement. In optical recording applications, the head may include amirror and an objective lens for focusing laser light on to an adjacentdisk surface. The slider is separated from the disk by a gas lubricationfilm that is typically referred to as an “air bearing.” The term “airbearing” is common because typically the lubricant gas is simply air.However, air bearing sliders have been designed for use in disk driveenclosures that contain helium, because an inert gas may not degradelubricants and protective carbon films as quickly as does oxygen. Heliummay also be used, for example, because it has higher thermalconductivity than air, and therefore may improve disk drive cooling.Also, because the air bearing thickness depends on the gas viscosity anddensity, the air bearing thickness may be advantageously reduced inhelium relative to air (all other conditions being the same).Furthermore, because helium has lower density than air, its flow (e.g.flow that is induced by disk rotation) may not buffet components withinthe disk drive as much, which may reduce track misregistration andthereby improve track following capability—facilitating higher datastorage densities.

Disk drive enclosures disclosed in the art to contain helium aretypically hermetically sealed in an attempt to prevent an unacceptablerate of helium leakage. Although some negligible amount of heliumleakage is unavoidable, a non-negligible amount of helium leakage isundesirable because it can alter the thickness of the gas lubricationfilm between the head and the disk, and thereby affect the performanceof the head. A non-negligible amount of helium leakage is alsoundesirable because it can alter the tribochemistry of the head diskinterface, possibly leading to degradation in reliability, head crashes,and associated data loss.

Certain disk drives that contain air may include a small opening in thedisk drive enclosure to allow a limited flow of air from the outsideenvironment, for example through a labyrinth path and/or a breatherfilter, to equalize the internal air pressure within the disk drive withthe outside air pressure. However, certain other disk drives thatcontain air may be hermetically sealed, with the disk drive enclosureunder some stress to maintain super-ambient or sub-ambient pressurewithin the disk drive.

Various methods and structures have been disclosed in the past tohermetically seal disk drive enclosures. Some of these have been toocostly, have required too much change to existing disk drivemanufacturing processes, and/or were not able to retain helium internalto the disk drive enclosure for sufficient time to ensure adequateproduct reliability. Others have made rework of disk drives (afterassembly) difficult or impractical, or had structural problems such asblistering of flexible seals due to gas pressure within the disk driveenclosure being temporarily or permanently super-ambient or sub-ambient.

Thus, there is a need in the art for a disk drive design that may bepractically hermetically sealed in a high volume and low costmanufacturing process, and/or that can retain air, helium, or anothergas internal to a disk drive enclosure for a sufficient period of timeto ensure adequate post-manufacture product reliability and lifetime.There is also a need in the art for a disk drive design that may betterresist excessive seal blistering and/or other structural problems thatmay result from the gas pressure within the disk drive being or becomingdifferent from the gas pressure outside of the disk drive enclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a disk drive according to theprior art.

FIG. 2 is a plan view of a disk drive with its foil seal removed toreveal features of the top cover, showing the general location of thecross-sectional views of FIGS. 3A-E.

FIG. 3A is a cross-sectional view of a portion of a disk drive, withfoil seal in place.

FIG. 3B depicts the cross-section of FIG. 3A, with the foil sealblistering over a channel in the top cover, because of a drop inexternal pressure.

FIG. 3C depicts the cross-section of FIG. 3B, after the blister hasundesirably delaminated a region of the foil seal to vent to a centralcavity of the disk drive enclosure.

FIG. 3D depicts the cross-section of FIG. 3C, after the foil seal hasre-adhered to the disk drive top cover adjacent the channel afterventing.

FIG. 3E depicts the cross-section of FIG. 3D, with foil seal tension andundesirable lateral displacement of the foil seal due to a subsequentincrease in external pressure.

FIG. 4A is a perspective view of a disk drive with its foil seal removedto reveal features of the top cover, which is capable of being sealedaccording to an embodiment of the present invention.

FIG. 4B is a zoomed in view of a portion of the disk drive of FIG. 4A.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 is an exploded perspective view of a disk drive 10 according tothe prior art. The disk drive 10 includes a head disk assembly (HDA) 12and a printed circuit board assembly (PCBA) 14. The HDA 12 includes adisk drive base 16 and cover 18 that together house disks 20. Each ofthe disks 20 may contain a plurality of concentric tracks for storingdata, disposed upon its opposing disk major surfaces between an innerradial extent 22 and an outer radial extent 24.

In the example of FIG. 1, a rotary spindle 26 is attached to the diskdrive base 16 of the HDA 12, and may include a disk mounting hub 27 uponwhich the disks 20 may be mounted. The rotary spindle 26 rotates thedisks 20 about a disk axis of rotation 28. The disks 20 may be stackedand separated with one or more annular disk spacers 21, and clamped tothe disk mounting hub 27 by a disk clamp 23. The HDA 12 further includesa head stack assembly (HSA) 30 pivotably attached to the disk drive base16 of HDA 12 by use of a pivot bearing cartridge 44 that is engagedwithin a bore of an actuator body 32. The pivot bearing cartridge 44 mayfacilitate the HSA 30 to rotate relative to HDA 12 about an actuatorpivot axis 46.

One or more actuator arms 36 may extend from the actuator body 32, andone or more head gimbal assemblies (HGA) 42 may be attached to a distalend of each actuator arm 36. Each HGA 42 may include a head 40 forreading and writing data from and to an adjacent disk surface. The HSA30 may further include a coil 50. The coil 50 may interact with one ormore magnets 54 attached to disk drive base 16 via a yoke structure 56,58, to form a voice coil motor for controllably rotating the HSA 30. TheHDA 12 also optionally includes a latch 52 pivotably mounted on the diskdrive base 16 to limit the rotational movement of the HSA 30.

In the example of FIG. 1, the PCBA 14 may include a servo control systemfor generating servo control signals to control the current through thecoil 50 and thereby position the HSA 30 relative to concentric tracksdisposed upon the surfaces of disks 20. The HSA 30 may be electricallyconnected to PCBA 14 via a flex cable 62 and a flex cable supportbracket 64 that attaches to the disk drive base 16.

FIG. 2 is a plan view of a disk drive 100, which includes a disk driveenclosure that includes a disk drive base 120, and a top cover 130. Thedisk drive 100 also includes a foil seal, but the foil seal is not shownin FIG. 2, so that features of the top cover 130 and the peripheral topface 122 of the disk drive base 120 can be seen.

FIGS. 3A-3E are cross-sectional views of a portion of the disk drive100, including a foil seal 150. FIG. 2 shows the location 3 of thecross-section of FIGS. 3A-3E. Now referring to FIGS. 2-3E, the diskdrive base 120 includes a central cavity 140 surrounded by a peripheralwall 124 and bounded by a cavity floor 142. The peripheral wall 124 hasa peripheral top face 122. The top cover 130 is disposed over thecentral cavity 140 to define a disk drive enclosure. The top cover 130has a central top face (e.g. adjacent to the label 130) that defines acentral top face plane 131. An outer periphery of the top cover 130optionally may be spaced from the peripheral wall 124 of the disk drivebase 120 by a peripheral clearance gap 144 that defines a gap width Pthat is preferably but not necessarily in the range of 0.1 mm to 1 mm.

A disk 320 is rotatably attached to the disk drive base 120 within thecentral cavity 140 and disposed within the disk drive enclosure formedby the disk drive base 120 and the top cover 130. The foil seal 150 isadhered to the central top face of the top cover 130, and optionallyalso to the peripheral top face 122 of the disk drive base 120 (with thefoil seal 150 spanning the peripheral clearance gap 144). The foil seal150 may be adhered to the central top face of the top cover 130 by anadhesive that may optionally comprise a conventional acrylic pressuresensitive adhesive layer having a thickness in the range 10 to 100microns. Such an adhesive may permit removal of the foil seal 150 fordisk drive rework that may become necessary during or after disk drivemanufacture, while otherwise retaining helium within the disk drive 100for a sufficient period to ensure adequate post-manufacture productreliability and lifetime.

The foil seal 150 may optionally include a continuous metal foil, and acontinuous adhesive layer coating the underside of the continuous metalfoil. In the present context, a metal foil is considered continuous ifit is one contiguous and monolithic foil sheet, rather than an assemblyof previously separate sub-regions. The foil seal 150 may be a puremetal or metal alloy foil that includes copper, aluminum, tin, and/orgold, preferably having a metal foil thickness in the range 2 to 100microns. Alternatively, the foil seal 150 may comprise a stainless steelfoil having a thickness in the range 2 to 40 microns. Such thicknessranges may advantageously allow the foil seal 150 to be flexible enoughto seal, and also have adequate robustness to avoid damage from diskdrive handling. Alternatively, but not necessarily, the foil seal 150may comprise a thin metal coating sputtered upon a polymer backingsheet.

As shown in FIG. 3B, the central top face of the top cover 130 mayinclude an outer channel 134 that is depressed towards the disk 320relative to the central top face plane 131 by a top cover channel depthd that is preferably but not necessarily in the range of 0.3 mm to 3 mm.The foil seal 150 covers the outer channel 134. As shown in FIG. 2, theouter channel 134 optionally follows an arcuate path that defines anouter arcuate radius R that is preferably but not necessarily less thanor equal to 38 mm. The central top face of the top cover 130 may furtherinclude an optional inner channel 136 that is depressed towards the disk320 relative to the central top face plane 131. The central top face ofthe top cover 130 may further include an optional connecting channel 138that is depressed towards the disk 320 relative to the central top faceplane 131.

In the example of FIG. 2, the inner channel 136 may follow an arcuatepath that is concentric with the arcuate path of the outer channel 134.The arcuate path of the inner channel 136 may define an inner arcuateradius r that is optionally less than the radius R of the outer channel134. The inner arcuate radius r may preferably but not necessarily begreater than or equal to 15 mm. The connecting channel 138 preferablybut not necessarily connects the inner channel 136 to the outer channel134.

In the example of FIGS. 2-3E, the top cover 130 is attached to the diskdrive base 120 by a plurality of screw fasteners 112. The foil seal 150preferably covers the plurality of screw fasteners 112. The foil seal150 is preferably not adhered to a bottom land 132 of the outer channel134, but spans the outer channel 134 to enclose a volume of gas (e.g.air, helium, etc). The outer channel 134 defines a channel width W thatis preferably but not necessarily in the range of 1 mm to 20 mm.

The enclosure of the disk drive 100 optionally may be helium-filled(i.e. the central cavity 140 may optionally enclose a substantialconcentration of helium gas). Practically, the concentration of enclosedhelium gas (e.g. versus remaining air) would be less than 100%initially, and would be expected to drop over the useful life of thedisk drive 100. Still, the disk drive 100 may be considered“helium-filled” throughout its useful life so long as it continues toenclose a substantial concentration of helium gas. Note also that 1.0atmosphere pressure of helium is not required for the disk drive 100 tobe considered “helium-filled.” For example, a helium-filled disk driveenclosure may initially enclose helium having between 0.3 to 1.0atmosphere partial pressure, and may also enclose air having between 0to 0.7 atmosphere partial pressure. In certain applications, it may bedesirable for at least 70% of the helium gas that is initially enclosedto remain enclosed after a 10 year useful life of the hermeticallysealed disk drive.

FIGS. 3A-E are related by depicting the same structure at sequentiallylater instances in time. For example, in FIG. 3B, the foil seal 150 isblistering over the outer channel 134 of the top cover 130, because of adrop in external pressure relative to that assumed in FIG. 3A. In FIG.3C the blister in the foil seal 150 has undesirably delaminated a regionof the foil seal 150 from adhering to the top cover 130, so that the gastrapped in the blister can vent to the central cavity 140 of the diskdrive enclosure. In FIG. 3D, the foil seal 150 has re-adhered to thedisk drive top cover 130 adjacent the outer channel 134, after venting.Finally, in FIG. 3E the foil seal 150 is subjected to tension andundesirable lateral displacement due to a subsequent increase inexternal pressure relative to that assumed in FIG. 3C.

The delamination of the foil seal 150 that is depicted in FIG. 3C, andthe displacement of the foil seal 150 that is depicted in FIG. 3E, areundesirable because they can lead to wrinkles and creases in the foilseal 150 that may allow an undesirable rate of leakage. Hence, certainpreferred embodiments of the present invention include structure topermit venting of the outer channel 134, without the venting pathrequiring blistering or delamination of the foil seal 150.

For example, FIG. 4A is a top perspective view of a disk drive 400 withits foil seal removed, that is capable of being sealed according to anembodiment of the present invention. FIG. 4B is a zoomed in view of aportion of the disk drive 400. The disk drive 400 includes a disk driveenclosure that includes a disk drive base 420, and a top cover 430. Thedisk drive 400 also includes a foil seal, but the foil seal is not shownin FIGS. 4A and 4B, so that features of the top cover 430 and theperipheral top face 422 of the disk drive base 420 will not be obscured.

In the embodiment of FIGS. 4A and 4B, an outer periphery of the topcover 430 optionally may be spaced from the peripheral top face 422 ofthe disk drive base 420 by a peripheral clearance gap 444. As shown inFIG. 4A, the central top face of the top cover 430 may include an outerchannel 434 that is depressed inwardly into the disk drive enclosurethat is formed by the top cover 430 and the disk drive base 420. Theouter channel 434 optionally follows an arcuate path about an axis ofrotation of an underlying disk, with such arcuate path defining an outerarcuate radius that is preferably but not necessarily less than or equalto 38 mm. However, non-arcuate paths for the outer channel 434 are alsocontemplated herein.

In the embodiment of FIGS. 4A and 4B, the central top face of the topcover 430 may further include optional inner and connecting channels 436and 438 that are depressed inwardly into the disk drive enclosure thatis formed by the top cover 430 and the disk drive base 420. The innerchannel 436 may optionally follow an arcuate path about an axis ofrotation of an underlying disk, which is concentric with the arcuatepath of the outer channel 434. However, non-arcuate inner channels arealso contemplated herein. In the embodiment of FIGS. 4A and 4B, thearcuate path of the inner channel 436 may define an inner arcuate radiusthat is optionally less than the radius of the outer channel 434. Theinner arcuate radius may preferably but not necessarily be greater thanor equal to 15 mm. The connecting channel 438 preferably but notnecessarily connects the inner channel 436 to the outer channel 434.

In the embodiment of FIGS. 4A and 4B, the outer and inner channels 434,436 may be vented to a central cavity of the disk drive base 420 by ahole 460 through a bottom land of the inner channel 436. Alternativelyor in addition, the outer and inner channels 434, 436 may be vented to acentral cavity of the disk drive base 420 by a hole through a bottomland of the outer channel 434. Alternatively or in addition, the outerand inner channels 434, 436 may be vented to a central cavity of thedisk drive base 420 by a hole through a bottom land of the connectingchannel 438. In this way, gas in the outer and inner channels 434, 436can be vented to the central cavity (e.g. to equalize pressure), via thehole 460 to permit venting of the outer and inner channels 434, 436without the venting path requiring blistering or delamination of anoverlying foil seal.

In the embodiment of FIGS. 4A and 4B, the hole 460 is round and maypreferably but not necessarily have a hole diameter in the range of 0.3mm to 2 mm. However, holes of other than circular shape are alsocontemplated herein. In certain embodiments, the hole 460 may prevent orreduce the undesirable delamination and/or displacement of an overlyingfoil seal that is depicted in FIGS. 3C and 3E.

In the foregoing specification, the invention is described withreference to specific exemplary embodiments, but those skilled in theart will recognize that the invention is not limited to those. It iscontemplated that various features and aspects of the invention may beused individually or jointly and possibly in a different environment orapplication. The specification and drawings are, accordingly, to beregarded as illustrative and exemplary rather than restrictive.“Comprising,” “including,” and “having,” are intended to be open-endedterms. “Preferably” is used herein to mean preferably but notnecessarily.

We claim:
 1. A disk drive comprising: a disk drive base comprising acentral cavity surrounded by a peripheral wall; and a top cover attachedto the disk drive base and disposed over the central cavity to define adisk drive enclosure, the top cover having a central top face thatdefines a central top face plane; a disk rotatably attached to the diskdrive base within the central cavity and disposed within the disk driveenclosure; and a foil seal adhered to the central top face; wherein thecentral top face of the top cover includes a first channel that has abottom land that is depressed towards the disk relative to the centraltop face plane, wherein the foil seal covers the first channel, andwherein the first channel is vented to the central cavity by a holethrough the bottom land of the first channel.
 2. The disk drive of claim1 wherein the bottom land of the first channel is depressed towards thedisk relative to the central top face plane by a top cover channel depthin the range of 0.3 mm to 3 mm.
 3. The disk drive of claim 1 wherein thefoil seal comprises a metal selected from the group consisting ofcopper, aluminum, and stainless steel.
 4. The disk drive of claim 1wherein the disk drive enclosure is helium-filled.
 5. The disk drive ofclaim 4 wherein the helium-filled enclosure encloses helium havingbetween 0.3 to 1.0 atmosphere partial pressure.
 6. The disk drive ofclaim 5 wherein the helium-filled enclosure also encloses air havingbetween 0 to 0.7 atmosphere partial pressure.
 7. The disk drive of claim1 wherein the foil seal includes a metal coating on a polymer backinglayer.
 8. The disk drive of claim 1 wherein the disk defines an axis ofdisk rotation, and the first channel follows a first arcuate path aboutthe disk axis of rotation that defines a first arcuate radius.
 9. Thedisk drive of claim 8 wherein the central top face of the top coverfurther includes a second channel that is depressed towards the diskrelative to the central top face plane, the second channel following asecond arcuate path about the disk axis of rotation that is concentricwith the first arcuate path.
 10. The disk drive of claim 9 wherein thecentral top face of the top cover further includes a third channel thatis depressed towards the disk relative to the central top face plane,the third channel connecting the second channel to the first channel.11. The disk drive of claim 1 wherein the first channel defines a firstchannel width in the range of 1 to 20 mm.
 12. The disk drive of claim 8wherein the first arcuate radius is in the range of 15 mm to 38 mm. 13.The disk drive of claim 1 wherein the hole is round and has a holediameter in the range of 0.3 mm to 2 mm.
 14. The disk drive of claim 1wherein the foil seal is adhered to the central top face by an adhesivelayer that comprises acrylic pressure sensitive adhesive having athickness in the range 10 to 100 microns.
 15. The disk drive of claim 1wherein the top cover is attached to the disk drive base by a pluralityof screw fasteners, and the foil seal covers the plurality of screwfasteners.
 16. The disk drive of claim 1 wherein the foil seal is notadhered to the bottom land of the first channel, but spans the firstchannel to enclose a volume of gas.
 17. The disk drive of claim 16wherein the gas comprises air or helium.
 18. The disk drive of claim 16wherein the gas is vented to the central cavity by the hole.